JP2005235739A - Fuel cell component and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell component wherein uniform coating having excellent corrosion resistance is applied to a contact part making contact with a gas and the like, and to provide a manufacturing method of the fuel cell component. …Ž<P>SOLUTION: This fuel cell component is a component having the contact part making contact with liquid into which the gas circulating in the inside of a fuel cell or a part of it is fused. After applying electrodeposition coating using electrodeposition paint to the contact part of the fuel cell component which is in contact with the gas, the electrodeposition paint applied on the contact part in contact with the gas and the like is baked on the fuel cell component, and is fixed as uniform coating. The electrodeposition coating is the most preferably applied with cation electrodeposition coating using cation type polyimide electrodeposition paint. …Ž<P>COPYRIGHT: (C)2005,JPO&NCIPI …Ž

Description

  The present invention relates to a fuel cell component having a contact portion with a gas flowing inside the fuel cell or a liquid in which a part thereof is dissolved, and a method for manufacturing the fuel cell component.

  In general, a fuel cell is composed of a fuel cell stack in which battery cells and separator plates are alternately arranged and stacked and held between a pair of end plates via a terminal plate and an insulating plate. ing. In the case of a polymer electrolyte fuel cell, the battery cell is configured by sandwiching a solid polymer membrane made of a proton-permeable polymer material between an air-side electrode and a hydrogen-side electrode that have both gas permeability and conductivity. Has been. Separator plates and end plates that are fuel cell components that make up the fuel cell and are involved in the construction of the gas flow path in the cell are the parts that contact the gas flowing through the fuel cell or a liquid in which a part thereof is dissolved (hereinafter referred to as (Referred to as “contact portion with gas etc.”).

  With the operation of the fuel cell, corrosive substances (for example, hydrofluoric acid) volatilize from the battery cell or part of it dissolves in moisture, generating corrosive gas and corrosive liquid (acidic water), It is known that they corrode contact portions with gas or the like of metal parts constituting the gas flow passage of the fuel cell (see, for example, Patent Document 2). For this reason, it is an important technical problem to improve the corrosion resistance at the contact portion of the metal parts constituting the fuel cell with the gas. In this connection, Patent Document 1 discloses that heat-resistant and acid-resistant polyethersulfone (PES) or polytetrafluoroethylene (fluorine) is used on the inner surface of the gas pipe in order to ensure corrosion prevention of the gas pipe of the fuel cell. It is proposed to cover with a resin) film. In Patent Document 1, PES is dissolved in dichloromethane (solvent), poured into a gas pipe, applied, and then evaporated, and fluorine resin is applied by electrostatic coating, and then heated to high temperature. By processing, a film is formed inside the gas pipe.

  However, in the film forming method used in Patent Document 1 (resin solution casting method or electrostatic coating method), when the shape of the fuel cell component is complicated, the coating film is uneven, that is, the film is not uniform. In addition, discontinuity in film formation is likely to occur, and many pinholes are easily formed in the film. Therefore, there is a drawback that sufficient corrosion resistance is difficult to obtain.

  Further, in the method of electrostatically coating the fluororesin disclosed in Patent Document 1, if there is a welded portion in the fuel cell component part and an oxide film generated during welding remains there, the residual oxide film is fluorine. There is a drawback in that the fluororesin does not adhere sufficiently at the welded portion and it is difficult to obtain corrosion resistance as a significant alienation factor for resin adhesion.

Japanese Patent Laid-Open No. 5-89903 (Summary and Examples) JP2003-142120A (paragraph 0003)

  An object of the present invention is to provide a fuel cell component in which a uniform coating excellent in corrosion resistance is applied to a contact portion with a gas or the like. Moreover, it is providing the manufacturing method of such a fuel cell component.

  In addition, even when a welded portion is included in a contact portion of a fuel cell component with a gas or the like, a fuel cell having a uniform coating with excellent corrosion resistance applied to the contact portion with the gas or the like including the welded portion It aims at providing a component and its manufacturing method.

  The present invention relates to a fuel cell component having a contact portion with a gas flowing in the fuel cell or a liquid in which a part thereof is dissolved, and the contact portion is provided with a coating formed by an electrodeposition coating method. It is a fuel cell component part characterized by the above-mentioned (Claim 1). More preferably, the contact portion is provided with a coating made of a polyimide electrodeposition paint formed by an electrodeposition coating method (claim 2). More preferably, the fuel cell component according to claim 1 or 2, wherein the base material of the fuel cell component is made of a casting (Claim 3). Furthermore, the contact portion of the fuel cell component includes a welded portion, and the contact portion including the welded portion is provided with a coating formed by an electrodeposition coating method. A fuel cell component according to claim 1 or 2 (claim 4).

  The present invention also relates to a method of manufacturing a fuel cell component having a contact portion with a gas flowing through the fuel cell or a liquid in which a part thereof is dissolved, and is a cation type with respect to the contact portion of the fuel cell component Production of a fuel cell component characterized by applying a cationic electrodeposition coating using a polyimide electrodeposition coating and then baking and fixing the cationic polyimide electrodeposition coating applied to the contact portion on the fuel cell component A method (claim 5). More preferably, the fuel cell component manufacturing method according to claim 5, wherein the base material of the fuel cell component is made of a casting (Claim 6). Further, the contact portion of the fuel cell component includes a welded portion, and the contact portion including the welded portion is subjected to cationic electrodeposition coating using a cationic polyimide electrodeposition paint. A fuel cell component manufacturing method according to claim 5 (claim 7).

(Action):
According to the fuel cell component of the present invention and the method of manufacturing the same, since the electrodeposition coating method is employed for forming a coating (protective film) on the surface of the contact portion of the fuel cell component with the gas or the like, Even in the case of a complicated shape, a uniform coating can be uniformly applied to the entire surface of the contact portion with the gas or the like. The uniformity of the protective film formed by the electrodeposition coating method is very high and there are almost no pinholes, so that the corrosion resistance of the contact portion with the gas or the like is greatly improved.

  In particular, the electrodeposition coating (more preferably cationic electrodeposition coating) is applied to the contact portion of the fuel cell component with the gas using a polyimide electrodeposition coating (more preferably cationic type polyimide electrodeposition coating). When a coating made of a paint is formed, the corrosion resistance of the contact portion with gas or the like is dramatically increased, and the corrosion resistance level is superior to that of the fluororesin coating.

  Furthermore, according to the present invention, even when the base material of the fuel cell component is made of a casting, excellent corrosion resistance can be obtained by coating the contact portion of the casting component with gas or the like by an electrodeposition coating method. Secured. In general, there are innumerable fine holes (hole diameter of 50 μm or less) that inevitably occur in the surface layer portion of a casting, and since these fine holes are present, uniform and continuous coating has been difficult. However, according to the present invention, a uniform and continuous coating can be applied to the entire surface of the contact part with the gas or the like of the cast part without being affected by the fine holes.

  Further, according to the present invention, even when the welded portion is included in the contact portion with the gas or the like of the fuel cell component, by applying the coating by the electrodeposition coating method to the contact portion including the welded portion, Good adhesion between the coating and the contact portion can be obtained, and relatively good corrosion resistance can be ensured.

  According to the fuel cell component of the present invention, the contact portion with the gas etc. of the fuel cell component by the electrodeposition coating method is coated with a uniform coating with excellent corrosion resistance, so the corrosion resistance of the contact portion with the gas etc. Is greatly improved. As a result, corrosion of the fuel cell gas distribution part (gas piping, etc.) is prevented or suppressed, and the service life of the fuel cell is prolonged, as well as weight reduction due to corrosion and the outflow of environmental pollutants (eg heavy metals). Is prevented as much as possible.

  According to the method for manufacturing a fuel cell component of the present invention, it is possible to easily and reliably manufacture a fuel cell component having a uniform coating excellent in corrosion resistance at a contact portion with a gas or the like.

  The present invention relates to a fuel cell component having a contact portion with a gas flowing inside the fuel cell or a liquid in which a part thereof is dissolved. Examples of such fuel cell components include a separator plate, an end plate, and a terminal plate (terminal) for constituting a so-called fuel cell stack. The base material of the fuel cell component may be a cast metal as well as a rolled metal material. Examples of casting materials include aluminum-based materials, iron-based materials, magnesium-based materials, copper-based materials, titanium-based materials, tin-based materials, and zinc-based materials. Of these, aluminum-based materials (for example, aluminum alloys) And iron-based materials (for example, stainless steel, cast steel, cast iron) are particularly preferred.

  In addition, the base material of the fuel cell component may be formed by joining a plurality of metal rolled materials by welding. The welding method for joining metal rolling materials is not specifically limited. However, an inert gas arc welding such as Tig welding is particularly preferable as a welding technique in the contact portion of the fuel cell component with the gas. According to the inert gas arc welding, it is possible to suppress the generation of an oxide film at the welded portion as much as possible, and to improve the adhesion of the coating formed by the electrodeposition coating method, and hence the corrosion resistance.

  The contact portion of the fuel cell component with the gas or the like is coated by an electrodeposition coating method. Since the fuel cell component of the present invention is made of metal, the electrodeposition coating method includes cation electrodeposition in which a negative voltage is applied to the object to be coated (fuel cell component) to deposit a positively polarized electrodeposition paint. It is preferable to employ a coating method.

  The electrodeposition paint used in the electrodeposition coating of the present invention is not particularly limited, but it is preferable to use a polyimide electrodeposition paint or a fluororesin electrodeposition paint. In particular, it has been confirmed by experiments that polyimide-based electrodeposition paints can ensure better corrosion resistance than the use of fluororesin-based electrodeposition paints even when the same electrodeposition coating is performed (Examples 3 and 4 described later). reference).

  As the polyimide-based electrodeposition paint, a cationic polyimide electrodeposition paint mainly composed of polyimide having a chemical structure as shown in the following chemical formula 1 is most preferable. In Chemical Formula 1, R represents an alkyl chain, and Ar represents an aromatic structure. This cationic polyimide electrodeposition coating has a glass transition temperature of about 200 ° C. (DSC measurement) and a 5% weight loss temperature of about 400 ° C. (TGA measurement), and has extremely high heat resistance. Further, the dielectric breakdown voltage of the cationic polyimide electrodeposition paint is about 1000 V, and has extremely high electrical insulation.

  When manufacturing fuel cell components, after applying cationic electrodeposition coating using a cationic polyimide electrodeposition coating to the contact portion of the fuel cell component with the gas, etc., it is applied to the contact portion with the gas. It is preferable that the cationic polyimide electrodeposition coating is baked and fixed on the fuel cell component. Since it is often necessary to secure a conductive surface or conductive portion in the fuel cell component, it is preferable to mask the conductive surface of the fuel cell component as necessary before applying electrodeposition coating. . The conditions for electrodeposition coating, the pretreatment and post-treatment methods for the object to be coated, the baking conditions for the electrodeposition paint, and the like are appropriately selected according to the properties of the electrodeposition paint used.

  Hereinafter, Examples 1 to 5 and Comparative Examples 1 to 3 in which the present invention is embodied in a metal end plate constituting a fuel cell stack will be described.

(Example 1):
In Example 1, an end plate made of a casting whose base material is made of an aluminum alloy was used. First, a portion of the end plate that does not constitute the gas pipe portion was masked with a mask material to prepare an end plate in which at least the constituent portion of the gas pipe was exposed. The end plate was thoroughly degreased and washed with ion exchange water or pure water. A water bath was prepared by diluting a cationic polyimide electrodeposition paint (product of Shimizu Corporation: Elecoat PI) with ion-exchanged water or pure water in an electrodeposition coating tank, and the bath temperature was adjusted to about 25 ° C. . The washed end plate is immersed in the polyimide electrodeposition paint water bath to connect a part of the end plate (electrode connection portion) to the negative electrode of the DC power supply device, and the carbon counter electrode immersed in the water bath is connected to the DC power source. It was connected to the positive electrode of the apparatus, and electrodeposition coating was applied at a voltage of 20 to 150 V for about 2 minutes. Then, the end plate taken out from the electrodeposition coating tank was washed with water, followed by air drying and preliminary drying (at 80 to 100 ° C. for about 10 minutes). And after removing the said mask material from the end plate, it moved to the heating apparatus, and the baking process (about 210 degreeC for 30 minutes) of the polyimide electrodeposition coating material was performed. Thus, an end plate made of an aluminum alloy casting in which a polyimide film having a film thickness of about 11 μm was formed on the gas piping component part was obtained.

(Comparative Example 1):
In Comparative Example 1, the same end plate made of an aluminum alloy casting was used as in Example 1. First, as in Example 1, a portion of the end plate that does not constitute the gas piping portion was masked with a mask material to prepare an end plate in which at least the constituent portion of the gas piping was exposed. The end plate was thoroughly degreased and washed with ion exchange water or pure water. Then, the end plate was immersed in a gold cyanide bath, and gold plating was applied to the exposed metal surface of the end plate by electroplating. In this way, an end plate made of an aluminum alloy casting in which a gold film having a thickness of about 11 μm was formed on the gas piping component part was obtained.

(Example 2):
In Example 2, a cast end plate whose base material is made of stainless steel (SUS316) was used. And like Example 1, it masks with the mask material with respect to the location which does not comprise the gas piping part of an end plate, and after washing with degreasing washing, ion-exchange water, or pure water, it is a cation type polyimide electrodeposition paint (made by Shimizu Corporation) Product: Elecoat PI) was painted by the electrodeposition coating method. However, the applied voltage value at the time of electrodeposition coating was made lower than that in Example 1. As in Example 1, the end plate taken out from the electrodeposition coating tank was washed with water, air blown, pre-dried, the mask material was removed from the end plate, and then the polyimide electrodeposition paint was baked (at about 210 ° C. For 30 minutes). In this way, an end plate made of a stainless steel casting in which a polyimide film having a film thickness of about 5 μm was formed on the gas piping component part was obtained.

(Comparative Example 2):
In Comparative Example 2, the same end plate made of a casting made of stainless steel (SUS316) as that used in Example 2 was used. First, as in Examples 1 and 2, a portion of the end plate that does not constitute the gas piping portion was masked with a mask material to prepare an end plate in which at least the constituent portion of the gas piping was exposed. The end plate was thoroughly degreased and washed with ion exchange water or pure water. Then, the end plate was immersed in a gold cyanide bath, and gold plating was applied to the exposed metal surface of the end plate by electroplating. Thus, an end plate made of a stainless steel casting having a gold film having a film thickness of about 9 μm formed on the gas pipe constituent part was obtained.

(Example 3):
In Example 3, an end plate made of a rolled material made of stainless steel (SUS316L) was used. And like Example 1, it masks with the mask material with respect to the location which does not comprise the gas piping part of an end plate, and after washing with degreasing washing, ion-exchange water, or pure water, it is a cation type polyimide electrodeposition paint (made by Shimizu Corporation) Product: Elecoat PI) was painted by the electrodeposition coating method. As in Example 1, the end plate taken out from the electrodeposition coating tank was washed with water, air blown, pre-dried, the mask material was removed from the end plate, and then the polyimide electrodeposition paint was baked (at about 210 ° C. For 30 minutes). Thus, an end plate made of a rolled stainless steel material in which a polyimide film having a film thickness of about 15 μm was formed on the gas piping component part was obtained.

(Example 4):
In Example 4, the same end plate as that used in Example 3 was made of a rolled material whose base material was stainless steel (SUS316L). First, as in Examples 1 and 3, a portion of the end plate that does not constitute the gas piping portion was masked with a mask material to prepare an end plate in which at least the constituent portion of the gas piping was exposed. The end plate was thoroughly degreased and washed with ion exchange water or pure water. Prepare a water bath in which a fluororesin-dispersed electrodeposition paint (product of Shimizu Corporation: Elecoat Nicelon CTR) is diluted with ion-exchanged water or pure water to an appropriate concentration in the electrodeposition coating tank. Adjusted to 25 ° C. The cleaned end plate is immersed in the fluororesin electrodeposition paint water bath to connect a part of the end plate (electrode connection part) to the negative electrode of the DC power supply, and the carbon counter electrode immersed in the water bath is connected to the DC It connected to the positive electrode of the power supply device, and applied electrodeposition for about 2 minutes at a voltage of 30 to 200V. Then, the end plate taken out from the electrodeposition coating tank was washed with water, and pre-dried (about 10 minutes at 80 to 100 ° C.) after air blowing. And after removing the said mask material from the end plate, it moved to the heating apparatus, and the baking process (about 210 degreeC for 30 minutes) of the fluororesin electrodeposition coating material was performed. Thus, an end plate made of a rolled stainless steel material in which a fluororesin film having a film thickness of about 15 μm was formed on the gas piping component part was obtained.

(Example 5):
In Example 5, as shown in the partially enlarged cross-sectional view of FIG. 4A, the ends of two rolled steel (11, 12) of stainless steel (SUS304) are attached to each other by TIG welding (13). An end plate based on the bonded one was used. In the end plate, the TIG welded portion (13) is included in the gas piping component. And like Example 1, it masks with the mask material with respect to the location which does not comprise the gas piping part of an end plate, and after washing with degreasing cleaning, ion-exchange water, or pure water, it is cationic type polyimide electrodeposition paint (made by Shimizu Corporation) Product: Elecoat PI) was painted by the electrodeposition coating method. As in Example 1, the end plate taken out from the electrodeposition coating tank was washed with water, air blown, pre-dried, the mask material was removed from the end plate, and then the polyimide electrodeposition paint was baked (at about 210 ° C. For 30 minutes). Thus, as shown in the partially enlarged cross-sectional view of FIG. 4B, a rolled stainless steel material in which a polyimide film (14) having a film thickness of about 9 μm is formed on the gas pipe constituent part including the TIG welded part (13). An end plate made of (Tig welded product) was obtained.

(Comparative Example 3):
In Comparative Example 3, the same base material as that used in Example 5 was bonded by TIG welding (13) with the ends of two rolled steel materials (11, 12) made of stainless steel (SUS304). An end plate was used. First, as in Example 5, a portion of the end plate that does not constitute the gas pipe portion was masked with a mask material, and an end plate in which at least the constituent portion of the gas pipe was exposed was prepared. The end plate was thoroughly degreased and washed with ion exchange water or pure water. Then, the end plate was immersed in a gold cyanide bath, and gold plating was applied to the exposed metal surface of the end plate by electroplating. Thus, an end plate made of a rolled stainless steel material (TIG welded product) in which a gold film having a film thickness of about 9 μm was formed on the gas piping component including the TIG welded portion (13) was obtained.

(Corrosion resistance test method):
Each end plate obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was subjected to a corrosion resistance test. The method of the corrosion resistance test was in accordance with Japanese Industrial Standard “Measurement Method of Anode Polarization Curve of Stainless Steel” (JIS-G0579). That is, a measuring device is prepared by combining a potentiostat, a potential sweep device, a recorder with a logarithmic converter, an electrolytic cell and a thermostatic chamber, and the electrolytic cell has a counter electrode (platinum electrode) electrically connected to the potentiostat. And a reference electrode (in this case SCE (saturated ginger electrode)). Further, the electrolytic cell was filled with a 20% aqueous sulfuric acid solution, the temperature of the solution was adjusted to 30 ° C., and nitrogen gas was blown in for about 1 hour for deoxygenation treatment. After immersing a test piece to be measured (electrically connected to a potentiostat) in a solution in an electrolytic cell, an anodic polarization curve was measured with a potentiostat and a potential sweep device. The potential sweep rate was 20 mV per minute. Then, the measured polarization curve was converted to SHE, and the converted curve was recorded on a semi-logarithmic recording paper (where voltage is a horizontal axis of a regular interval scale and current density is a vertical axis of a logarithmic scale). The measurement results for Example 1 and Comparative Example 1 are shown in FIG. 1, the measurement results for Example 2 and Comparative Example 2 are shown in FIG. 2, the measurement results for Example 3 and Example 4 are shown in FIG. The measurement results for No. 5 and Comparative Example 3 are shown in FIG.

(Consideration of corrosion resistance test results):
The anodic polarization curve can serve as an index for judging whether the corrosion resistance of the metal test piece is good or bad. In other words, the smaller the current density appears in the predetermined potential sweep range, the better the corrosion resistance. Conversely, the larger the current density, the lower the corrosion resistance.In other words, corrosion tends to proceed when it comes into contact with corrosive gas or liquid (corrosion rate is fast). ).

The measurement results in FIG. 1 (comparison between Example 1 and Comparative Example 1), the measurement results in FIG. 2 (Comparison between Example 2 and Comparative Example 2), and the measurement results in FIG. 5 (Example 5 and Comparative Example 3) In contrast, the polyimide film of the present invention (Examples 1, 2 and 5) over a wider voltage range than the gold film (Comparative Examples 1, 2 and 3) known as a general corrosion-resistant film. It was found to show high corrosion resistance. Particularly in Examples 1 and 2, although the base material of the end plate is made of a casting which is generally considered difficult to form a uniform film, a polyimide film (film thickness is about 5 to 11 μm) by the electrodeposition coating method. It is noteworthy that a very high level of corrosion resistance can be ensured so that the current density is 0.01 μA / cm ² or less.

Further, from the measurement results of FIG. 3, according to the end plate provided with the polyimide film (Example 3) formed by the electrodeposition coating method and the fluororesin film (Example 4) formed by the electrodeposition coating method, It has been found that a high level of corrosion resistance can be ensured so that the current density is 0.1 μA / cm ² or less. In particular, from the comparison between Example 3 and Example 4, it is noteworthy that the polyimide film is superior to the fluororesin film in terms of ensuring corrosion resistance.

  From the result of Example 5 (see FIG. 5), even if the welded portion (13) is present in the gas piping component of the stainless steel end plate, by forming the polyimide film (14) by the electrodeposition coating method, It has been found that a relatively good level of corrosion resistance can be secured.

The graph which shows the result of the corrosion resistance test about Example 1 and Comparative Example 1. FIG. The graph which shows the result of the corrosion resistance test about Example 2 and Comparative Example 2. FIG. The graph which shows the result of the corrosion resistance test about Example 3 and Example 4. FIG. (A) is a partial expanded sectional view of the TIG welded product of the stainless steel rolling material in Example 5, (B) is a partially expanded sectional view when the TIG welded product is coated. The graph which shows the result of the corrosion resistance test about Example 5 and Comparative Example 3. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11,12 ... Rolled material, 13 ... Welded part, 14 ... Polyimide film (coating).

Claims (7)

  A fuel cell component having a contact portion with a gas flowing through the fuel cell or a liquid in which a part of the gas is dissolved, and the contact portion is provided with a coating formed by an electrodeposition coating method A fuel cell component characterized by.   A fuel cell component having a contact portion with a gas flowing inside the fuel cell or a liquid in which a part thereof is dissolved, wherein the contact portion is a coating made of a polyimide electrodeposition paint formed by an electrodeposition coating method A fuel cell component characterized by the above.   The fuel cell component according to claim 1 or 2, wherein the base material of the fuel cell component is made of a casting.   2. The contact portion of the fuel cell component includes a welded portion, and the contact portion including the welded portion is coated with a coating formed by an electrodeposition coating method. Or a fuel cell component according to 2; A method of manufacturing a fuel cell component having a contact portion with a gas flowing through the fuel cell or a liquid in which part of the gas is dissolved,
After the cationic electrodeposition coating is applied to the contact portion of the fuel cell component using a cationic polyimide electrodeposition paint, the cationic polyimide electrodeposition coating applied to the contact portion is baked and fixed on the fuel cell component. A method for producing a fuel cell component, characterized by comprising:   6. The method of manufacturing a fuel cell component according to claim 5, wherein the base material of the fuel cell component is made of a casting.   6. A contact portion of the fuel cell component includes a welded portion, and the contact portion including the welded portion is subjected to cationic electrodeposition coating using a cationic polyimide electrodeposition coating. A method for producing a fuel cell component as described in 1 above.

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